4091989 has 4 divisors (see below), whose sum is σ = 4464000. Its totient is φ = 3719980.

The previous prime is 4091959. The next prime is 4091993. The reversal of 4091989 is 9891904.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 4091989 - 2⁵ = 4091957 is a prime.

It is a super-2 number, since 2×4091989² = 33488747952242, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4091909) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 185989 + ... + 186010.

It is an arithmetic number, because the mean of its divisors is an integer number (1116000).

Almost surely, 2^4091989 is an apocalyptic number.

It is an amenable number.

4091989 is a deficient number, since it is larger than the sum of its proper divisors (372011).

4091989 is a wasteful number, since it uses less digits than its factorization.

4091989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372010.

The product of its (nonzero) digits is 23328, while the sum is 40.

The square root of 4091989 is about 2022.8665304463. The cubic root of 4091989 is about 159.9477563806.

It can be divided in two parts, 40 and 91989, that added together give a palindrome (92029).

The spelling of 4091989 in words is "four million, ninety-one thousand, nine hundred eighty-nine".